Copper wire in magnetic field

A piece of stiff copper wire hangs from a metal between the jaws of a u-shaped magnet and its free end dips into a pool of mercury. Mercury is connected to a positive terminal.
piece of stiff wire will move:
A towards the south pole
B towards the north pole
C to the right towards the support
D to the left towards the power supply
If someone can just tell me what the mercury does i should be right.
I'm assuming it would go to either the north or south pole.

Well, you know that your current is either flowing up or down (depending on how you've set up the battery). The mercury, as 'Four' stated, is a conductor and will allow for the completion of the circuit. Knowing that the B-Field (magnetic field) is travelling from North to South, use that nifty right hand rule to find the force acting on the current carrying wire. This rule corresponds with the equation F=b.I.l, where force is the direction of your palm, the B-Field is the direction of your fingers and I, current, is the way in which your thumb is pointing.